Street 350 Small Block - Cam Comparison

Flat-Tappet Or Roller Cam? We Build A Budget Street 350 To Put Them To The Test.

It's often said that money makes the world go around. And it's true to some extent. Our hobby is often ruled by the almighty dollar. We crave a set of three-piece forged wheels, but our wallet steers us toward budget-friendly cast wheels. We shop for the best deal and agonize about the price, but can we go too far? This happens with engine builds all the time. To save a couple of hundred bucks, we stuff in cast pistons, only to regret the decision when we get the itch to strap on a nitrous system. We lose the bottom end of our engine because a factory bolt failed when a set of high-end bolts would have cost us under $50. Sure, we should be frugal with our hard-earned cash, but it's not really a savings if it costs you a lot more down the line.

For this story we wanted to build your typical 350 small-block, an engine as iconic to our hobby as Rolex is to watches. The idea was to put it together the way your average gearhead would. Spend cash where it made sense and try to save a buck when it wouldn't cause problems later on.

The biggest choice involved the valvetrain. Solid cams are great for big power and race cars, but if you plan on logging tons of miles, adjusting valve lash can get old. Hydraulic flat-tappet cams are pretty much maintenance free and very economical, but oiling issues can flatten out a lobe in the blink of an eye. Hydraulic roller cams are what all the new engines run, but they can be pricey. Or are they? Sure, they cost more compared to flat-tappet equivalents, but if you're spending three to four grand on a new mill, is another $500 going to put you in hock? If your cam goes flat, any savings you enjoyed by going flat tappet will evaporate. The hydraulic roller arrangement is more reliable, and you won't be screwed if you forget to pour in a bottle of additive when you change your oil like you would be with a flat-tappet setup.

To test this out, we built a middle-of-the-road 350, dynoed it with a flat-tappet cam, and tossed in a hydraulic roller cam to see what would happen.

The heart of our build is this crank. According to eagle, its ESP cast steel crankshafts have a higher ductility than OE units and feature .092-inch radii on all journals for added strength. They can also use OE-style bearings. Brian Taube of Eagle Specialty Products told us this package is rated for 500 hp at 6,500 rpm. Eagle also treated the crank, rods, and piston tops with its new ESP Armor finishing process. This process results in a more durable surface and stronger parts, and the slick surface sheds oil better.

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Eagle can balance the entire rotating assembly on its Hines equipment. This saved us the hassle of having it done locally and let us get to the assembly stage that much faster. Eagle also sent us the properly weighed flywheel. Eagle is known for high-quality connecting rods, and these forge 6.000-inch 5130 SIR I-bean units are no exception. They're bushed to work with full-floating piston pins. The rods also utilize ARP cap screw fasteners and have alignment sleeves for easier assembly. They forged pistons are Mahle slugs and come coated right out of the box. The choice to run forged pistons means we're good to go if we want to toss on a 125 shot of nitrous for the track.

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At first we tried to find an early 350 block for our build, but everything we found was either too expensive or too worn out. After speaking with the guys over at AA Midwest, we found that we're not the only ones having this problem since they are seeing fewer and fewer nice early blocks as well. They suggested a later-model block, in this case from 1986. They are plentiful, in excellent condition, and can be had for a decent price. This four-bolt main block set us back $250 and included the seal retainer needed for the later one-piece main seal blocks. AA Midwest also offers an adapter so you can run a two-piece seal crank in a newer block. Here you can see the block after we cleaned it and had it rough-honed.

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Street 350 Small Block - Cam Comparison

When assembling an engine, being organized is critical. Andy Mitchell of Outlaw Racing Engines in Upland, California, laid out all the parts before mating the pistons to the rods using the supplied spring clips. We also made sure to use plenty of assembly lube, in this case from Torco.

Before honing the block, Mitchell likes to confirm the size of the pistons. Attention to details during the machining process will pay big dividends in the final engine's reliability and power output.

The first step in prepping the block for assembly is boring and honing out the cylinders. We rough-honed the bores out .025 inch and then finished them to .030 inch. It's a good idea to use a torque plate during the hone process. This way the cylinder will be true after the heads are bolted on, and the rings will seat quickly.

With the main bearings installed, Tim laid the Eagle crank in place and secured it with a set of ARP main bolts (PN 134-5202, $31.95). We could have used the old bolts, but we liked the added insurance of running the considerably stronger ARP stuff. Tim then torqued the bolts to 75 lb-ft using the assembly lube provided by ARP.

With the crank cinched down, we slid in the new Comp Extreme Energy hydraulic flat-tapped bump stick (PN 12-246-3, $119.95). Specs for the cam are 230/236 at .o5o-inch and .490 lift with an LSA of 110. It can't be overstated how important assembly lube is for this install if you don't want to end up with a flat lobe on your cam.

We installed the Comp Magnum double-roller timing chain (PN 2100, $27.95) using ARP bolts (PN 234-1001, $6.88). Since this is a newer style block, we had to clearance the metal just a bit so the chain wouldn't rub. With this done, we could tape off the short-block and give it a few coats of Chevy orange paint.

After bolting on the oil pan, we flipped the engine over and dropped in the Comp High-Energy hydraulic lifters (PN 812-16, $72.95). Again, we used lots of assembly lube. Notice that late-model block is all set up to run roller parks (red arrows).

We also pieced up an oil pump from Summit (PN SES-3-60-08-005, $44.95). The pump included the pickup and driveshaft, so it was a pretty good deal. For a little added a insurance we put a half bottle of Torco lube in the oil pump. Again, lubrication is life for a flat-tapped valvetrain, We ditched the multi-piece oil pan gasket that came in the Fel-Pro set (PN FPP-2802, $109.95).

Tim then set the Weiand Stealth Air-Strike intake in place. The dual-plane aluminum intake is perfect for the street and only set us back $200. The manifold features a high-rise isolated runner design that helps keep the intake charge cooler.

These Comp Magnum roller-tip rockers (PN 1416-16, $157.95) are a good balance between budget and performance. Their 1.6 ratio will give us a bit more lift, and the roller tip will let the valvetrain work more efficiently. With the rockers in place, we were able to check what pushrod length we needed, which turned out to be 7.800 inches.

Lastly, we bolted on this 6.25-inch TCI Rattler balancer using an ARP fastener (PN 134-2501, $19.95). The rattler is a pendulum absorber that helps control vibration and crankshaft twist. The design doesn't rely on being filled with fluid and is pretty much maintenance free. We also picked up the matching TCI timing pointer.

With the flat-tappet engine assembled, we took it over to Westech Performance Group for some time on its Superflow dyno. After breaking in the cam and setting the timing, we made a few pulls and managed to get 375 hp at 5,500 rpm and 409 pounds of torque at 3,800 rpm from the little 350. The cam profile was lumpy and had less than 11 inches of vacuum at 1,000 rpm.

Then we pulled the flat-tappet parts out of the engine and slid in a roller cam. The cam was one we had in the shop, and at 218/224 with .570 lift and an LSA of 113, it was pretty tame.

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